diff --git a/tests/qos/files/mellanox/qos_param_generator.py b/tests/qos/files/mellanox/qos_param_generator.py
index 5f7fc6cade3..3399d511214 100644
--- a/tests/qos/files/mellanox/qos_param_generator.py
+++ b/tests/qos/files/mellanox/qos_param_generator.py
@@ -102,11 +102,11 @@ def calculate_parameters(self):
         xon = {}
         xon['pkts_num_trig_pfc'] = pkts_num_trig_pfc
         xon['pkts_num_dismiss_pfc'] = pkts_num_dismiss_pfc
-        xon['pkts_num_hysteresis'] = pkts_num_hysteresis
+        xon['pkts_num_hysteresis'] = pkts_num_hysteresis + 16
         if self.asic_type == 'spc2':
             xon['pkts_num_margin'] = 2
         elif self.asic_type == 'spc3':
-            xon['pkts_num_margin'] = 0
+            xon['pkts_num_margin'] = 3
         self.qos_params_mlnx['xon_1'].update(xon)
         self.qos_params_mlnx['xon_2'].update(xon)
 
@@ -114,8 +114,8 @@ def calculate_parameters(self):
         wm_pg_headroom['pkts_num_trig_pfc'] = pkts_num_trig_pfc
         wm_pg_headroom['pkts_num_trig_ingr_drp'] = pkts_num_trig_ingr_drp
         wm_pg_headroom['cell_size'] = self.cell_size
-        if self.asic_type == 'spc1':
-            wm_pg_headroom['pkts_num_margin'] = 1
+        if self.asic_type == 'spc3':
+            wm_pg_headroom['pkts_num_margin'] = 3
         else:
             wm_pg_headroom['pkts_num_margin'] = 2
 
diff --git a/tests/saitests/sai_qos_tests.py b/tests/saitests/sai_qos_tests.py
index afd9b828027..d09e172babe 100644
--- a/tests/saitests/sai_qos_tests.py
+++ b/tests/saitests/sai_qos_tests.py
@@ -1578,11 +1578,13 @@ def runTest(self):
         # send packets
         try:
             # send packets to trigger pfc but not trek into headroom
-            send_packet(self, src_port_id, pkt, pkts_num_leak_out + pkts_num_trig_pfc)
+            send_packet(self, src_port_id, pkt, pkts_num_leak_out + pkts_num_trig_pfc - margin)
             time.sleep(8)
             q_wm_res, pg_shared_wm_res, pg_headroom_wm_res = sai_thrift_read_port_watermarks(self.client, port_list[src_port_id])
             assert(pg_headroom_wm_res[pg] == 0)
 
+            send_packet(self, src_port_id, pkt, margin)
+
             # send packet batch of fixed packet numbers to fill pg headroom
             # first round sends only 1 packet
             expected_wm = 0